<!DOCTYPE html>
<html>
<head>
	<title>null和undefined的区别</title>
</head>
<body>
	<p id="demo"></p>
	<script>
		document.getElementById('demo').innerHTML =
		typeof undefined + "<br>" +
		typeof null + "<br>" +
		(null == undefined) + "<br>" +
		(null === undefined);
	</script>

</body>
</html>